What is Diabetes Mellitus?

The Difference Between Diabetes Mellitus and Diabetes Insipidus

Mellitus means "sweet urine" because the excess sugar in the bloodstream "spills" into the urinary tract. Photographers Choice RF/Getty Images

The term "mellitus," as in diabetes mellitus literally means “honey-sweet.” Diabetes mellitus was first identified as a disease associated with "sweet urine," because when blood glucose is elevated (hyperglycemia), it spills glucose into the urine. Diabetes mellitus is different from the less common diabetes insipidus.

What Is Diabetes Mellitus?

Diabetes mellitus is the more common condition and is what is generally referred to as simply “diabetes.” Diabetes is a Greek word that means "one that straddles" or goes to the bathroom a lot.


Diabetes mellitus is characterized by an excess of blood glucose, or blood sugar, that builds up in the bloodstream because the body is not able to adequately process the sugar taken in through food. High blood sugar is an abnormal state for the body and creates specific symptoms and possible long-term health problems if blood sugar is not managed well.

The disease diabetes mellitus has been recorded throughout history, since Egyptian times. It was given the name diabetes by the ancient Greek physician Araetus of Cappodocia. The full term, however, was not coined until 1675 in Britain by Thomas Willis, who rediscovered that the blood and urine of people with diabetes was sweet. This phenomenon had previously been discovered by ancient Indians.

Related: What Is Sugar Diabetes?

What is Diabetes Insipidus?

Diabetes insipidus is characterized by excessive urination and thirst, as well as a general feeling of weakness.

While these can also be symptoms of diabetes mellitus, in diabetes insipidus blood sugar levels are normal (and there's no sugar in the urine). Diabetes insipidus is a problem of fluid balance caused by a problem with the kidneys, where they can't stop the excretion of water. Polyuria (excessive urine) and polydipsia (excessive thirst) occur in diabetes mellitus as a reaction to high blood sugar.

There Are Three Main Types of Diabetes Mellitus:

  • Type 1 diabetes occurs when the pancreas stops or nearly stops producing the hormone insulin. Insulin is needed to enable blood glucose to be used for energy by the body. People with type 1 diabetes must take daily insulin injections. Type 1 diabetes has also been referred to as insulin-dependent diabetes and juvenile diabetes.
  • Type 2 diabetes occurs when the body is unable to make effective use of the insulin the pancreas does make. This is often referred to as insulin resistance. Obesity is a major cause of insulin resistance in both adults and children. Type 2 diabetes has also been called non-insulin dependent diabetes and adult-onset diabetes.
  • Gestational diabetes occurs in women who have high blood sugar during pregnancy but have not been diagnosed with diabetes previously. After delivery of the baby, many women see their blood sugar return to normal. Some women will go on to develop type 2 diabetes.

For more information on diabetes mellitus, find lots of related articles here.

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